#9572 - yaustar - Sat Aug 09, 2003 5:15 am
I have an idea how to set them but am new to the whole 'bits' and 'bit shifting'.
would I define them as:
| Code: |
#define BG_PRIORITY(n) ((n)<<1)
|
and add it to:
| Code: |
temp = bg->size | (bg->charBaseBlock<<CHAR_SHIFT) | (bg->screenBaseBlock<<SCREEN_SHIFT)
| bg->colorMode | bg->mosaic | bg->wraparound | bg->bg_priority;
|
While on the topic of backgrounds, do text backgrounds wraparound no matter what?
Thanks for your time[/code]
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#9573 - tepples - Sat Aug 09, 2003 5:32 am
Close. You're supposed to shift left by the number of the LOWEST order bit in the field. In the case of BG priority, the lowest order bit is bit 0, so | Code: |
| #define BG_PRIORITY(n) ((n) << 0) |
A non-trivial example might be sprite priority, which occupies bits 11 and 10 of a sprite's attribute 2. | Code: |
| #define OAM_PRIORITY(n) ((n) << 10) |
And yes, text backgrounds always wrap. You can make a text background not wrap by setting a window and telling the background to draw only within the window.
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#9588 - yaustar - Sat Aug 09, 2003 3:19 pm
thanks, that explains a lot
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#9600 - yaustar - Sun Aug 10, 2003 2:49 am
how would I change the priority on the fly, i.e. after initialisation.
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#9616 - niltsair - Sun Aug 10, 2003 11:26 pm
You retrieve the old 16bits value with a mask, leaving out the 2 bits concerning priority. You then 'or' this value with your new shifted priority value.
Say priority are bit 3&4 (I don't remember them offhand)
*bgRegValX = ( bgRegValX & 0xFFE7) | ( newPrioVal << 3);
(1111 1111 1110 0111 = 0xFFE7)
#22531 - jhinders - Wed Jun 23, 2004 8:12 pm
| tepples wrote: |
And yes, text backgrounds always wrap. You can make a text background not wrap by setting a window and telling the background to draw only within the window. |
how exactly would you set a window and tell the background to only draw within it?
#22535 - Miked0801 - Wed Jun 23, 2004 9:23 pm
No text backgrounds do not always wrap. There is a bit you set in the BG control register that tells it to wrap or fill 0 color. I don't have it handy, but could look it up if needed.
#22536 - poslundc - Wed Jun 23, 2004 9:52 pm
I'm fairly positive that bit only does anything for rotation backgrounds.
Dan.
#22537 - jhinders - Wed Jun 23, 2004 9:53 pm
| Miked0801 wrote: |
| No text backgrounds do not always wrap. There is a bit you set in the BG control register that tells it to wrap or fill 0 color. I don't have it handy, but could look it up if needed. |
according to the documentation i have you can't set that bit for BG0 and BG1.
#22538 - Miked0801 - Wed Jun 23, 2004 11:38 pm
Ok, strange - our engine is always playing with that bit. I'll have to go in and see if it is just being ignored or whatever on our side.
#22541 - tepples - Thu Jun 24, 2004 12:46 am
| jhinders wrote: |
| how exactly would you set a window and tell the background to only draw within it? |
Peruse this.
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